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Cosmic microwave radiation from observations of interstellar CN rotational temperature, rotational exitation by H I region H atoms and excitation by slow electrons and slow protons in H II region
Models for analyzing CN violet radiation effects behind shock waves in air contaminated with carbon-bearing compounds
Chemical model for CN nonequilibrium radiant emission intensity profiles in shock heated mixture of N and carbon dioxide
The basis and techniques are presented for generating opacity probability distribution functions for the CN molecule (red and violet systems) and the C2 molecule (Swan, Phillips, Ballik-Ramsay systems), two of the more important diatomic molecules in the spectra of carbon stars, with a view to including these distribution functions in equilibrium model atmosphere calculations. Comparisons to the CO molecule are also shown. T he computation of the monochromatic absorption coefficient uses the most recent molecular data with revision of the oscillator strengths for some of the band systems. The total molecular stellar mass absorption coefficient is established through fifteen equations of molecular dissociation equilibrium to relate the distribution functions to each other on a per gram of stellar material basis.
Previous accurate dipole moment calculation techniques are modified to be applicable to higher excited states of symmetry. The self-consistent fields and configuration interactions are calculated for the X(2)Sigma(+) and B(2)Sigma(+) states of CN. Spin hyperfine constants and spin density at the nucleus are considered in the context of one-electron operator properties. The values of the self-consistent field and configuration interaction for the spin density are compared with experimental values for several diatomic molecules.
A detailed non-LTE analysis of solar CN spectra strongly suggest a revised carbon abundance for the sun. We recommend a value of log carbon abundance = 8.35 plus or minus 0.15 which is significantly lower than the presently accepted value of log carbon abundance = 8.55. This revision may have important consequences in astrophysics.
A 20 kW electric-discharge pumped CN laser oscillating on the A(2) Pi-X(2) Sigma molecular system is presented. Excitation is by a simple longitudinal discharge struck through HCN vapor. Twenty kW peak power is generated in a 150 nsec full-width half-maximum pulse. Two lasing bands were observed in the A-X system: the (0,1) and (0,2) bands near 1.42 and 2.0 microns respectively. Both P and Q branches are active in the two bands, with Q bands stronger. Peak laser energy is 3 mJ. Products of UV photolysis of HCN, electron impact excitation of HCN, and other possible excitation mechanisms and laser efficiency are discussed.
A survey of 73 sources has been made in the emission lines of N2H(+) and HCO(+), including detailed maps of four sources (Ori A, OMC-2, DR 21 OH, and NGC 6334). These data are combined with equally extensive data for HCN and CN to make a detailed study of the spatial relationship of these four species. Actual abundance ratios are shown to vary, often sharply, over small scale lengths (of the order of 1 arcmin) within the mapped sources. Excitation temperatures also vary. All four species appear to be subthermally excited. The abundance ratios and their spatial variations are interpreted in terms of ion-molecular formation and destruction processes. It is concluded that the relative abundances of CO may be considerably lower in some regions than previously believed. No evidence is found for variations in the C/O ratio over small scale lengths in Ori A. The degree of ionization of the Ori A molecular cloud may be significantly different from that of other molecular clouds.
Infrared spectrophotometry of the R-type carbon star HD 19557 is presented. Two unusual spectroscopic features are seen: a 3.1 micron band is lacking and a 2.8 micron band is present. Identifications are proposed for three previously unreported stellar absorption bands with electronic sequences of C2, CN, and C2H. The latter is proposed to be responsible for the 2.8 micron feature. The atmospheric structure of the star is studied with synthetic spectra, and an effective temperature between 2600 K and 3000 K is suggested. No SiC emission is seen at 11.3 microns, indicating that grain formation is not a viable process around the star. The lack of dust in R stars may suggest a salient difference between R and N types.
The effects of the production of the radicals CN and C2H from the dissociation of HCN and C2H2 by ambient UV photons in the outer envelope of IRC +10216 are investigated. The spatial distribution of the radicals and their observable millimeter emission-line characteristics are calculated from the inferred abundances of the progenitor species in the envelope of IRC +10216 using photochemical and radiative transfer models. These are compared with available observations to examine whether photoproduction is a possible explanation of the observed emission from these species. The results suggest that the variable abundances induced by photodestruction of their progenitors do affect the observed emission from the radicals.
Pulsed laser photolysis of C2N2 at 193 nm has been used as a source of CN radicals in both the v-double-prime = 0 and v-double-prime = 1 levels. Individual rovibronic levels of these radicals were measured as a function of time with a tunable dye laser. From these measurements the rate constants for the reaction of each of these vibrational levels with H2, O2, CO, CO2, N2, HCN, C2N2, and CH4 have been determined. Some enhancement in the rate constant with vibrational energy which could not be ascribed to quenching was observed for O2, CH4, and H2. Only vibrational quenching was observed for HCN, N2, CO2, CO and C2N2. In the CO case the vibrational quenching rate appears to be significantly enhanced by complex formation during the quenching process.
The radial Haser scale lengths for the production and destruction of C2 and CN are calculated on the basis of brightness profiles for comets Bennett 1970 II and Kohoutek 1973 XII, applying the Monte Carlo particle-trajectory model of Combi and Delsemme (1980). Findings reported include C2/CN ratio independent of heliocentric distance, C2 ejection velocity from its parent molecule about 0.5 km/s, and 1-AU photochemical lifetime 31,000 s for the C2 parent molecule and 120,000 s for C2.
Measurements of the far-infrared lines of forbidden O III 51.8 microns, 88.4 microns, and forbidden N III 57.3 microns are presented for 13 H II regions covering a wide range in Galactocentric distance. These lines are used to measure the variation of N(2+)/O(2+) with Galactic radius from the center out to 12 kpc. It is argued that this ratio is indicative of the elemental ratio N/O. It is shown that the line flux ratio 57.3 microns forbidden N III/51.7 microns forbidden O III is nearly equal to the N(2+)/O(2+) abundance ratio and is only weakly dependent on nebular conditions. The derived N(2+)/O(2+) values show an inverse correlation with distance from the Galactic center. N(2+)/O(2+) tends to increase as the H II region electron temperature decreases, a behavior consistent with a model of Galactic enrichment in which N-14 is secondary to primary O-16, a scenario that is the natural result of CN processing.
Three spectra of Comet Halley in the 0.86 to 1.37-micron wavelength region have been obtained. On December 4, 1985, the 0-0, 1-1, 1-0, and 2-1 transitions of the red system of CN were detected using a 13 arcsec aperture centered on the nucleus of the comet. The 0-0 and 1-1 transitions were also observed in the coma at positions 20 arcsec from the nucleus. A line to continuum ratio of 0.25 was observed for the 0-0 transition at the position of the nucleus of the comet. A ratio of 1.5 was observed at the off-nucleus positions. On April 28, 1986, an upper limit to the strength of the 0-0 transition was obtained.
Radiative lifetimes have been measured for the stable vibrational levels of the A 1 sigma - electronic state of C2N2. They range from 1.3 microsec for the 4(sub 0)(sup 1) level to 0.66 microsec for the 1(sub 0)(sup 1) 4(sub 0)(sup 1) level and in general decrease with increasing vibrational excitation. Self-quenching rate constants range from gas kinetic to ten times that. Foreign gas quenching rates are slower. Observation of emission from the 1(sub 0)(sup 1) 4(sub 0)(sup 1) level sets a lower limit for the heat of formation of CN of 439.11 kJ/mol.
High-SNR high-resolution (R = 150,000-170,000) optical spectra of interstellar CN toward Zeta Per are presented. Fits to the data yield a value of 1.25 + or - 0.02 km/s for the R(O) linewidth parameter b along this line of sight. The column densities of the level populations are directly determined from the convolution of the instrument response function with a model which is then fitted to the data. Tex = 2.79 + or - 0.03 K is obtained along this line of sight.
From P/Halley long slit spectroscopic exposures on 12 dates, extending from Oct. 1985 to May 1986, spatial profiles were obtained for emissions by C2, CN, NH2, and OI(1D). Haser model scale lengths were fitted to these data. The extended time coverage allowed the checking for consistency between the various dates. The time varying production rate of P/Halley severely affected the profiles after perihelion, which is shown in two profile sequences on adjacent dates. Because of the time varying production rate, it was not possible to obtain reliable Haser model scale lengths after perihelion. The pre-perihelion analysis yielded Haser model scale lengths of sufficient consistency that they can be used for production rate determinations, whenever it is necessary to extrapolate from observed column densities within finite observing apertures. Results of scale lengths reduced to 1 AU are given and discussed.
The detection of CN emission the spectrum of (2060) Chiron not only underscores its cometary nature, but represents, at a heliocentric distance in excess of 11 AU, the most distantly detected instance of a cometary gas species. These observations are noted to be consistent with a driving of Chiron's outgassing by isolated outbursts of CO2 from a small fraction of Chiron's surface. If dusty particles or icy grains are dragged out by the gas with unit dust-to-gas mass ratio, outbursts need occur only once every several months. Such small-surface outgassings appear to characterize comets which have made many passages close to the sun.